I cant play, i cant install, i cant repair, i cant unninstall. i cant do nothing with de game.

I already deleted the game folder, I already restarted gog galaxy, I already rebooted the PC, nothing work.

The game is shown as installed by gog galaxy, how to remove it from the list and install again?

Try downloading the offline backup installer and reinstall it that way.
Then try to run it again. Make sure all the required libraries and external installers install too (DirectX, .NET whatever).

So many galaxy problem threads...